rcbo

[paulrayner]

hi guys just been out to a job with a faulty rcbo and i noticed that when you swiched on the rcd (high integraty board) the rcbo tripped . the rcbo was feeding another board. has anybody come across this before? is this due to harmonic currents? any thoughts would be greatfull

 

[supasparxs]

hi guys just been out to a job with a faulty rcbo and i noticed that when you swiched on the rcd (high integraty board) the rcbo tripped . the rcbo was feeding another board. has anybody come across this before? is this due to harmonic currents? any thoughts would be greatfull

Am I missing something here?
do you mean you have one RCD controlling an RCBO?

if so as you have one RCD controlling another it is random which will trip.
The RCD closer to the feed needs to have a time lag setting on it.

Richard

 

[paulrayner]

no its a wylex high integrety board with 2 rcd & 2 rcbo. the faulty rcbo was feeding another board, which has no rcd protection (all mcb's) What I dont understand is why after doin a ramp on other rcd's when turned back on the faulty rcbo tripped with no load whatsoever . Incidently i couldent even do a ramp on the faulty rcbo it just tripped as soon as i turned on the machine . the faulty rcbo would hold with no load but as soon as you flicked a switch it would trip all ins resistances were fine

 

[Graeme Harrold]

no its a wylex high integrety board with 2 rcd & 2 rcbo. the faulty rcbo was feeding another board, which has no rcd protection (all mcb's) What I dont understand is why after doin a ramp on other rcd's when turned back on the faulty rcbo tripped with no load whatsoever . Incidently i couldent even do a ramp on the faulty rcbo it just tripped as soon as i turned on the machine . the faulty rcbo would hold with no load but as soon as you flicked a switch it would trip all ins resistances were fine

Did you conduct an insulation test with the RCBO connected????

 

[paulrayner]

no dont be daft

 

[Spudnik]

Sounds like the usual borrowed neutral to me.

These usually hold on until you either energise the other RCD or a load is put on it.

 

[paulrayner]

It's definatly not a borrowed neutral & its been up and running fine for over 18 months this is one of those things i just cant get my head round

 

[The Truth]

if the flying neutral lead from the rcbo is connected to the correct neutral bar then there is no explanation for that rcbo trippng as you described short of it being faulty. ... being wylex and made from rice paper it probably broke as you took it out of the box.

 

[paulrayner]

if the flying neutral lead from the rcbo is connected to the correct neutral bar then there is no explanation for that rcbo trippng as you described short of it being faulty. ... being wylex and made from rice paper it probably broke as you took it out of the box.

You dont rate wylex much then? I must admit ive been using them off & on about 2 yrs now and in that time i've had a couple of dodgy mcb's & rcd's I also use sq D never had a problem with them apart from the wholesalers price. Going back to the original problem even if it is faulty WHY should it do this ?

 

[The Truth]

no terrible stuff...once upon a time before the recent model ..the consumer units were rock solid and good pieces of kit....infact so were MK when the mcbs and RCD's were manufactered by Merlin Gerin.. now the only manufacturers that live up to there name are Hager and square D / merlin / legrand etc but then they always have been the best quality. Even crabtree are the same nasty build quality now. blah blah blah waht was the question? Why should you change the faulty rcbo? i think the answer is in the question no? its worth a shot to rule it out

 

[supasparxs]

hmmmmmm

as it's a high intergraty board there are other RCD's that you maybe able to borrow for test purposes.
why don't you move the circuit temporary onto another RCD/RCBO just for testing.
That way you will be able to alliminate the RCBO out of the equation as far as fault finding.
the work your way down the cable until you find the fault.....

Richard

 

[paulrayner]

no terrible stuff...once upon a time before the recent model ..the consumer units were rock solid and good pieces of kit....infact so were MK when the mcbs and RCD's were manufactered by Merlin Gerin.. now the only manufacturers that live up to there name are Hager and square D / merlin / legrand etc but then they always have been the best quality. Even crabtree are the same nasty build quality now. blah blah blah waht was the question? Why should you change the faulty rcbo? i think the answer is in the question no? its worth a shot to rule it out

allready have done and switching on the other rcd,s dosent trip the rcbo so why did the faulty one trip with no load whatsoever on it when you switched the rcd's back on????????????? I don't understand why? if there was a borrowed neutral I could understand it.Ii'm comming to the conclusion after much thought that this one is going to beat me and I dont like it. I really would like to get to the bottom of it

 

[supasparxs]

allready have done and switching on the other rcd,s dosent trip the rcbo so why did the faulty one trip with no load whatsoever on it when you switched the rcd's back on????????????? I don't understand why? if there was a borrowed neutral I could understand it.Ii'm comming to the conclusion after much thought that this one is going to beat me and I dont like it. I really would like to get to the bottom of it

I had a similar thing on the Arndale Center (doing site temps).
The MDU worked fine, add a single phase supply and the RCD trips.
(merlin equipment inside)
I never did find the fault, I pulled 50 meters of armoured from another MDU and it worked.

sometimes fault never want to be found

Richard

 

[The Truth]

if its an internal fault to the rcbo / rcd then unless you have a thorough knowledge in the design and spec of those things then forget about it. it could be totally non electrical anyway..just a plain old mechanical fault..which are far more common....leave it alone

 

[paulrayner]

many thanks to all you guys who posted replys and sugestions. I've rung the customer up and i'm going back tomorrow afternoon to re test the whole installation just for my own peace of mind cos its buggin me will let you know how I get on , once again many thanks

update:
Been back and tested the whole installation again And I can't find a single thing wrong with it so I put the faulty RCBO back in and got the same problem .
The only conclusion that it can be is the Faulty rcbo.
needless to say that it still dosen't explain why thefaulty rcbo trips when you turn any of the 2 rcd's back on ?????
anyway i'm gonna leave it at that. an unanswered puzzle. will sleep tonight
many thanks again to all who responded